The present invention relates to a method and apparatus for analyzing a fluid that includes at least one liquid phase, contained in a tubular conduit; and more particularly to a method and apparatus for analyzing a fluid that includes a liquid phase, contained in a tubular conduit, using the sonic Stoneley wave.
Many industrial activities involve an analysis of fluids that include at least one liquid phase, contained in a tubular conduit. In one such activity, viz. providing drilling and production services to the oil industry, one may be particularly interested in providing an early detection of gas intruding in the mud during drilling, or a detection of gas presence and bubble distribution in drill stem testing, or in obtaining production or injection profiles, or in analyzing flowing slurries or mud cuttings. Other activities include measuring the characteristics of flowing fluids that include a liquid phase, involved in industrial processes and in distribution systems.
Many different techniques have been proposed to measure flow characteristics of fluids, i.e. liquids, gases, and combinations thereof (multiphase fluid), contained in tubular conduits. For example, some known techniques are based on sensing and correlating local pressure fluctuations, and on sensing the pressure field set up by a venturi or vortex element. A number of other well known techniques are based on the propagation of sonic or ultrasonic energy in a flowing fluid.
Examples of techniques for determining fluid velocity that involve the use of sonic energy propagating in the fluid are disclosed in the following U.S. Pat. Nos. 1,881,543, issued Oct. 11, 1932 to Hartig et al.; 2,151,203, issued Mar. 21, 1939 to Hartig; 2,274,262, issued Feb. 24, 1942 to Wolff; 2,534,712, issued Dec. 19, 1950 to Gray; and 4,003,252, issued Jan. 18, 1977 to Dewath. The apparatus disclosed in the Hartig et al. U.S. Pat. No. 1,881,543 uses sound tubes inserted through the tube into the fluid flow and measures fluid velocity with a reflection-compensated continuous wave, or "CW" measurement technique. The apparatus disclosed in the Hartig U.S. Pat. No. 2,151,203 uses ports along a tube and measures fluid velocity with a travel time technique. The apparatus disclosed in the Wolff patent uses ports along a tube and measures air velocity with a CW technique. The apparatus disclosed in the Gray patent introduces sonic pulses into an unconfined air stream and determines air velocity with a travel time technique. The apparatus disclosed in the Dewath patent uses transducers recessed in the acoustically damping liner of a tube, which achieves a fluid flow conduit substantially devoid of protuberances and cavities. A CW technique is used to determine fluid velocity.
Another nonintrusive instrument that overcomes some of the disadvantages of the Dewath apparatus is disclosed in U.S. Pat. No. 4,445,389, issued May 1, 1984 to Potzick et al. An acoustic technique is discussed which involves the use of wavelengths longer than the cutoff wavelength of the conduit, such that when the acoustic waves reach the receivers, the cutoff spatial modes will have decayed nearly to zero and only the fundamental waves will be present. A CW technique is used to determine fluid velocity and sound velocity.
Most of these techniques are said to be applicable to fluids generally, including liquids such as oil and water. yet, none of these techniques has been adapted to oilfield service applications, where the fluid is a liquid or a multiphase fluid including a liquid phase. The techniques that rely on extensive use of damping materials are impractical for most environments encountered in oilfield services, while the other techniques either fail or are not reliable when used to investigate a liquid or multiphase fluid.
The technique disclosed in U.S. Pat. No. 4,236,406, issued Dec. 2, 1980 to Reed et al., involves the use of ultrasonic energy directed through the fluid being investigated, for determining fluid sound velocity. The technique is said to be capable of metering water content in an oil-water system by the determining sonic velocities in the flowing oil-water mixture. Other ultrasonic techniques are disclosed in U.S. Pat. No. 2,991,650, issued July 11, 1961 to Katzenstein et al. Various propagation paths, including one approximately along the longitudinal axis of a portion of a pipe, are illustrated and described.
Ultrasonic techniques have been adapted for use in oilfield servies, as disclosed in U.S. Pat. No. 4,452,077, issued June 5, 1984 to Siegfried; and U.S. Pat. No. 3,130,808, issued Apr. 28, 1965 to Walker, Jr. et al. These techniques share a disadvantage with the non-borehole ultrasonic techniques, viz. they sample only a limited region of the fluid under investigation. Hence, they are not advantageous in applications for which a measurement independent of flow profile is desired. The technique disclosed in the Siegfried patent further is disadvantageous in being adversely affected by tool eccentricity, irregularities in the well casing, and particulates and gas phases in the borehole liquid.